<template>
  <div id="app" class="mydiv">


  <router-link to="/a" active-class="select">去a</router-link>
  <router-link to="/b" active-class="select">去b</router-link>
   
  <router-view></router-view>

  </div>
</template>

<script>
//  import HelloWorld from './components/HelloWorld.vue'

export default {
  name: 'App',
  components: {
  }
}
</script>

<style>
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
.mydiv{
  display: flex;
  flex-direction: column;
}
.select{
  background: red;
}
</style>
